Conventional slot antennas include a slot or aperture formed in a conductive plate or surface. The slot forms an opening to a cavity, and the shape and size of the slot and cavity, as well as the driving frequency, contribute to a radiation pattern. The length of the slot depends on the operating frequency and is typically about λ/2 and inherently narrowband. Conventional slot antennas are linearly polarized and can have an almost omnidirectional radiation pattern. More complex slot antennas may include multiple slots, multiple elements per slot, and increased slot length and/or width.
Slot antennas are commonly used in applications such as navigational radar and cell phone base stations. They are popular because of their simple design, small size, and low cost. Improved designs are constantly sought to improve performance of slot antennas, increase their operational bandwidth, and extend their use into other applications.